1. Field of the Invention
The present invention relates to a target detecting device, a target detecting method, and a target detecting program, which detect a target. More specifically, the present invention relates to a target detecting device, a target detecting method, and a target detecting program, which detect a target by emitting and receiving a laser beam.
2. Background Information
A burglarproof system typically has a detecting device which detects a human who intrudes into a predetermined guarding area (hereinafter, referred to as an “intruder”), and an alarm generating device which generates an alarm based on a detected result. The detecting device is an infrared sensor or a laser sensor, which detects the intruder using a light beam. The alarm device permits lighting or flashing of an illuminating lamp and sounding of an alarm buzzer or a siren. The alarm device transmits an alarm signal to a facility to be guarded or a remote place. The burglarproof system further has an image displaying device which images the guarding area to display its image.
To increase the detecting accuracy of a target, the laser sensor using a laser beam has been received attention as the detecting device. The laser sensor has a laser pulse generator (for example, including a laser diode), and a photodetector (for example, including an avalanche photodiode). The laser pulse generator generates a laser pulse wave. The photodetector detects a reflection light reflected from the target. Flight time, that is, reflection time is computed to measure a distance from the laser sensor to the target. A scan mechanism portion may further be provided to rotate a laser optical axis, and in this case, two-dimensional distance information can be obtained. Therefore, a wide monitoring area can be set (see U.S. Pat. No. 3,011,121).
The detecting device used for the burglarproof system need to be set so as to reliably detect a human and not to detect a small animal such as a dog or a cat. The detecting device often detects the small animal as the human to output a human body detecting signal, resulting in lowering of the reliability of the burglarproof system. To prevent misdetection, it is considered that the difference in height between the human and the small animal is used to install the laser sensor horizontally at about the height of a waist of an adult. In this case, the human is detected and the small animal is not detected. When the laser sensor is installed horizontally in a low position and an obstruction of about the height of the human exists between the laser sensor and the guarding area, it is difficult to avoid occurrence of a plurality of undetectable areas in the guarding area.